Infrared thermal velocimetry in MEMS-based fluidic devices

Most MEMS (microelectromechanical system) devices are made of silicon which is transparent at infrared wavelengths. Utilizing this infrared transparency of silicon, infrared thermal velocimetry was developed to measure the velocity in MEMS based fluidic devices. The method uses an infrared laser to generate a short heating pulse in a flowing liquid. An infrared camera records the radiative images from the heated flowing liquid and the steady flow velocity is obtained from consecutive radiative images. A wide range of the velocity (1 cm/s-1 m/s or higher) in silicon (or other materials that are transparent to infrared radiation) microchannels can be measured. Numerical simulations have been carried out and are in good agreement with the experiments. Parametric studies have been carried out for different channel dimensions and laser characteristics.